An orally available, human, immunoglobulin G1 (IgG1) kappa, monoclonal antibody directed against the p19 protein subunit of interleukin-23 (IL-23), with immunomodulating activity. Upon administration, guselkumab binds to the p19 subunit of IL-23, thereby blocking the binding of IL-23 to the IL-23 receptor. This inhibits IL-23-mediated signaling and the differentiation of CD4-positive T-cells into Th1 and Th17 cells. This prevents Th1- and Th17-mediated immune responses and inhibits the production of pro-inflammatory cytokines. This may prevent or reduce symptoms and severity of immune-mediated inflammatory disorders. IL-23 plays a key role in the regulation of inflammation and the immune system, and modulates the release of various pro-inflammatory cytokines and chemokines. It is upregulated in various immune-mediated inflammatory disorders.